Synergistic herbicidal combination

ABSTRACT

A mixture of the herbicides napropamide and butam has been found to exhibit synergistic results, particularly in pre-emergence surface application or pre-plant incorporation, and for controlling weeds in the presence of a rapeseed crop.

This invention relates to a herbicidal combination of two knownherbicides, napropamide and butam, each of which is known to beeffective for certain purposes, but which combination has been found topossess unexpected synergistic properties.

Napropamide, 2-(α-napthoxy)-N,N-diethylpropionamide, ##STR1## is acommercial herbicide sold under the registered trademark Devrinol® andis described as a herbicide with both pre-emergence and post-emergenceactivity in U.S. Pat. Nos. 3,480,671, 3,718,455, and 3,998,880, forinstance. These patents also contain methods of preparing this compound.

Butam, N-benzyl-N-isopropylpivalamide, ##STR2## is described, forinstance, in U.S. Pat. Nos. 3,707,366 and 3,974,218, which containmethods for its preparation. The compound is known to be an effectivepre-emergence herbicide for controlling annual grassy weeds in certaincrops, including soybeans, rapeseed, cotton and others.

It has now been found that a combination of napropamide and butam,containing these two substances in a weight ratio respectively of about2:1 to about 1:2, possesses synergistic activity in controlling weeds,in general, and in the presence of a rapeseed crop. This synergisticactivity is exhibited most particularly at application rates of fromabout 0.25 to about 1.5 pounds per acre (about 0.28 to about 1.68 ha) ofeither or both compounds.

The following examples demonstrate the synergistic herbicidal responseof such compositions.

EXAMPLE 1 (Greenhouse Evaluation--Pre-emergence Surface Treatment)

This example demonstrates the synergistic response of combinations ofnapropamide and butam in combined pre-emergence surface application to avariety of weeds planted in the presence of a rapeseed crop.

Flats were filled to a depth of 3 inches (7.6 cm) with loamy sand soilcontaining 50 parts per million (ppm) each of a fungicide and 18-18-18fertilizer. Seeds of rapeseed (Brassica napobrassica) and six weedspecies were planted in individual rows using one species per row acrossthe width of the flat. The seeds were covered with soil. The weeds usedwere annual ryegrass (Lolium multiflorum), barnyardgrass (Echinochloacrusgalli), green foxtail (Setaria viridis), lambsquarter (Chenopodiumalbum), pigweed (Amaranthus retroflexus), and wild buckwheat (Polygonumconvolvulus). The seeds were planted to give about 20 to 50 seedlingsper row after emergence, depending on the size of the plants.

Compositions were prepared for testing by weighing out 20 mg.respectively of napropamide and butam, and dissolving each portion in 3ml. of acetone which contained 1% polyoxyethylene sorbitan monolaurateemulsifying agent. The solution was then sprayed uniformly on the soilin the flat one day after planting the seeds, at application ratesranging from 0.25 to 0.5 pounds per acre (0.28 to 0.56 kg/ha). Aftertreatment the flats were placed in a greenhouse at a temperature of70°-85° F. and watered by sprinkling. Two weeks after treatment thedegree of injury or control was determined by comparison of untreatedcheck plants of the same age. The injury rating, on a scale of 0 to100%, was recorded for each species as percent control, with 0%representing no injury and 100% representing complete kill.

The results of these tests are contained in the following Table I. Underthe heading "O" are given the ratings for the compounds applied asobserved. Under the heading "E" are provided the expected results forcombinations of the two herbicides, based on the response for eachherbicide alone, derived from this data using Limpel's formula, namely,##EQU1## where X=the observed percent injury when one of the herbicidesis used alone and

Y=the observed percent injury when the other herbicide is used alone.

This formula is contained in the article "Weed Control byDimethylchloroterephthalate Alone and in Certain Combinations," Limpelet al., Proc. NEWCC., Vol. 16, pp. 48-53 (1962). When the observedresult exceeds the result which would have been expected using thisformula, synergism is demonstrated.

                                      TABLE I                                     __________________________________________________________________________                  Annual                                                                            Barn-           Wild                                                  Rape-                                                                             rye-                                                                              yard                                                                              Fox-                                                                              Lambs-                                                                            Pig-                                                                              Buck-                                       Naprop-   seed                                                                              grass                                                                             grass                                                                             tail                                                                              quarter                                                                           weed                                                                              wheat                                       amide                                                                              Butam                                                                              O E O E O E O E O E O E O E                                         __________________________________________________________________________    0.25 --   0    0  20   0  20   0   0                                          0.50 --   0   45  65  50  70  50  30                                          --   0.25 0   20  30  20  10   5   0                                          --   0.50 0   30  65  20  30  40   0                                          0.25 0.25 0 0 50                                                                              20                                                                              80                                                                              44                                                                              30                                                                              20                                                                              65                                                                              28                                                                              50                                                                               5                                                                              10                                                                               0                                        0.25 0.50 0 0 78                                                                              30                                                                              90                                                                              72                                                                              60                                                                              20                                                                              68                                                                              44                                                                              40                                                                              40                                                                              30                                                                               0                                        0.50 0.25 0 0 85                                                                              56                                                                              85                                                                              75                                                                              78                                                                              60                                                                              75                                                                              73                                                                              55                                                                              52                                                                              50                                                                              30                                        __________________________________________________________________________

EXAMPLE 2 (Field Tests, Pre-plant Incorporation)

Sprayable solutions containing napropamide and butam were prepared bymixing a wettable powder containing approximately 50 weight %napropamide with an emulsifiable concentrate containing approximately 6pounds per gallon (0.72 kg per liter) butam, and water. The solution wassprayed on field test plots in various locations in France, WestGermany, and Great Britain, at an application rate of 0.75 kg/ha (0.67lb/acre) napropamide and 1.44 kg/ha (1.28 lb/acre) butam. Afterspraying, the soil was filled to incorporate the herbicidal mixture, andwas then planted with rapeseeds. Other plots at the same locations weresimilarly treated with napropamide and butam alone, at the same ratesbefore planting, and one plot was left untreated as a check. Tests wereconducted during the fall season.

Undesirable vegetation which appeared in the plots included:

France: volunteer barley, volunteer wheat, Alopercurus myosuroides,Matricaria chamomilla, Sinapis arvensis, Veronica persica, Veronicahederaefolia

Germany: volunteer barley, Alopecurus myosuroides, Galium aparine,Lamium amplexicaule, Matricaria chamomilla, Stellaria media, violaarvensis

Great Britain: volunteer barley, Alopecurus myosuroides, Matricariaspp., Senecio vulgaris, Stellaria media

Results of these tests are contained in the following Tables II-IV.Control of weeds and phytotoxic effect on crops were determined byvisual comparison with the untreated check plots. In all cases, thecombination of napropamide and butam resulted in little or no damage tothe rapeseed crop.

Synergistic control effects were found in West Germany in volunteerbarley and in France of Sinapis arvensis. In a number of the tests, thecontrol of a given weed by one of the two compounds was sufficientlyhigh so as to leave no effective possibility of improvement at theapplication rates. Limpel's Formula was used as above in determiningsynergistic activity.

                                      TABLE II                                    __________________________________________________________________________    FRANCE                                                                        Compounds and                                                                            Control, %                                                         Application Rates                                                                        Volunteer                                                                           Volunteer                                                                           Alopecurus                                                                           Matricaria                                                                          Sinapis                                                                            Veronica                                                                           Veronica                        (kg/ha)    barley                                                                              wheat myosuroides                                                                          chamomilla                                                                          arvensis                                                                           perisca                                                                            hedeaefolia                     __________________________________________________________________________    Napropamide, 0.75                                                                        100   56    95     87    50   90   96                              Butam, 1.44                                                                              79    79    97     87     0   85   39                              Napropamide, 0.75 +                                                                      96    79    98     87     76* 86   98                              Butam, 1.44                                                                   __________________________________________________________________________     *Expected Control  50%                                                   

                                      TABLE III                                   __________________________________________________________________________    WEST GERMANY                                                                  Compounds and                                                                            Control, %                                                         Application Rates                                                                        Volunteer                                                                           Alopecurus                                                                           Galium                                                                            Lamium Matricaria                                                                          Stellaria                                                                          Viola                           (kg/ha)    barley                                                                              myosuroides                                                                          aparine                                                                           amplexicaule                                                                         chamomilla                                                                          media                                                                              arvensis                        __________________________________________________________________________    Napropamide, 0.75                                                                        40    50     20  43     78    71   10                              Butam, 1.44                                                                              60    50     60  46     61    77   10                              Napropamide, 0.75 +                                                                       95*  70     40  71     94    93    43**                           Butam, 1.44                                                                   __________________________________________________________________________     *Expected control  76%                                                        **Expected control  20%                                                  

                                      TABLE IV                                    __________________________________________________________________________    GREAT BRITAIN                                                                 Compounds and                                                                            Control, %                                                         Application Rate                                                                         Volunteer                                                                           Alopecurus                                                                          Matricaria                                                                          Senecio                                                                            Stellaria                                   (kg/ha)    barley                                                                              myosuroides                                                                         spp.  vulgaris                                                                           media                                       __________________________________________________________________________    Napropamide, 0.75                                                                        25    74    59    87   54                                          Butam, 1.44                                                                              54    79    14     0   60                                          Napropamide, 0.75+                                                                       66    90    66    86   66                                          Butam, 1.44                                                                   __________________________________________________________________________

Compositions containing the two herbicides napropamide and butam may beprepared in a number of conventional ways. Butam is a colorless oil,insoluble in water but very soluble in ethanol, benzene and toluene, andis commercially marketed in the form of an emusifiable concentrate.Napropamide is a solid and is commercially marketed in several formsincluding granular, wettable powder, and flowable (concentrated aqueoussuspension). Formulations or compositions for applying the twoherbicides in combination may be prepared, for instance, by mixing awettable powder containing napropamide (50 weight percent) with anemulsifiable concentrate containing butam, in water, to prepare asprayable solution. The amounts of water, napropamide and butam, areselected so as to provide solutions containing the desired ratio ofnapropamide to butam and for application at the desired rate.

Alternatively, a herbicide composition containing napropamide and butamcan be prepared from the technical grade herbicides, with suitableadjuvants, and then mixed with water to form a sprayable solution. Anexample of such a composition is:

    ______________________________________                                        Component               Weight %                                              ______________________________________                                        napropamide, technical grade (93% pure)                                                               14.2                                                  butam, technical grade (95% pure)                                                                     33.3                                                  1,1,1-trichloroethane   47.6                                                  surfactants             4.9                                                   Total                   100.0                                                 ______________________________________                                    

What is claimed is:
 1. A synergistic herbicidal composition comprising amixture of herbicidally effective amounts of napropamide and butam, in aweight ratio of between about 2:1 and about .[.1:2.]..Iadd.1:2.4.Iaddend..
 2. A composition according to claim 1 in which theweight ratio of napropamide to butam is about 2:1.
 3. A compositionaccording to claim 1 in which the weight ratio of napropamide to butamis about 1:1.
 4. A composition according to claim 1 in which the weightratio of napropamide to butam is about 1:2. .Iadd.5. A compositionaccording to claim 1 in which the weight ratio of napropamide to butamis between about 2:1 to about 1:2..Iaddend.